"OK" (also spelled "okay", "ok", or "O.K.") is a word denoting approval, acceptance, agreement, assent, or acknowledgment. "OK", as an adjective, can also express acknowledgment without approval. "OK" has frequently turned up as a loanword in many other languages.As an adjective, "OK" means "adequate", "acceptable" ("this is OK to send out"), "mediocre" often in contrast to "good" ("the food was OK"); it also functions as an adverb in this sense.